Abstract
This study investigated whether reproductive success is affected by the intensity of neighborhood aggregation of adults in the tropical tree Shorea laxa. We focused on three processes in the early reproductive stages: seed maturation; seed survival (categorizing sound seed, predation by insects and predation by vertebrates) in pre-seed dispersal; and seedling survival in the post-seed dispersal stage. We used a model selection procedure to examine the aggregation effect on reproductive success. The intensity of neighborhood aggregation was represented by the neighborhood aggregation index, which contains the adult number within a specific radius and the distances to neighboring adults (weight of proximity). Then, we evaluated the models exhaustively with the aggregation index having different scales (radius and weight of proximity) to assess the scale on which aggregation had significant effects. In particular, the best effective neighborhood scale, which is defined as the scale of the index in the model with minimum Akaike information criterion, was examined to compare those scales among processes. We found that the probability of seed maturation, seed survival and seedling survival decreased with the aggregation index at specific scales. This suggests that aggregation influenced reproductive success negatively in both the pre- and post-seed dispersal stages. However, the selected radii differed among processes: >200 and 130 m in pre- and post-seed dispersal stages, respectively. The selected weight of proximity also seemed to have a weak effect on all processes and was not different among processes.
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Acknowledgments
The authors thank to Ms. L. Chong (Forest Research Centre, Sarawak) for her permission and assistance for us to conduct this work in Sarawak. We are also grateful to Dr. K. Kitajima and an anonymous reviewer for valuable suggestions for our early manuscript. Dr. S. Sakai, Dr. T. Kenta and members of laboratory of forest biology in Kyoto University also gave us valuable suggestions for this study. We also thank Dr. M. Aiba and Mr. B. Jingan for field work assistant. This study was financially supported by the Grant for the Biodiversity Research of the 21st Century COE, MEXT Japan (A14), research grant from Showa Shell Sekiyu and the JSPS Research Fellowship for Young Scientists for Y. Takeuchi.
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An erratum to this article can be found at http://dx.doi.org/10.1007/s10265-009-0288-7
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10265_2009_265_MOESM1_ESM.pdf
Fig. S1. Estimated coefficients of the NAI in each model for seed fate models; x-axis radius k meters (10 ≤ k ≤ 300 per 5 m), y-axis weight of proximity l (0 ≤ k ≤ 2 per 0.05). a Seed maturation, b seed survival, (b-1 sound seeds, b-2 predation by insects, b-3 predation by vertebrates). Solid line indicates 0 (PDF 362 kb)
10265_2009_265_MOESM2_ESM.pdf
Fig. S2. The relationship between reproductive success and NAI in the best models. a Proportion of immature seeds, b mature seeds (b-1 proportion of sound seeds, b-2 proportion of seeds predated by insects, b-3 proportion of seeds predated by vertebrates) (PDF 341 kb)
10265_2009_265_MOESM3_ESM.pdf
Fig. S3. AIC values for seedling survival models including the NAI. a Seedling survival ~ NAI + water + light, b seedling survival ~ NAI + water, c seedling survival ~ NAI + light, d seedling survival ~ NAI. x-axis Radius k meters (30 ≤ k ≤ 300 per 5 m), y-axis weight of proximity l (0 ≤ k ≤ 2 per 0.05). The solid line indicates AIC values of the null model that does not contain the NAI (PDF 375 kb)
10265_2009_265_MOESM4_ESM.pdf
Fig. S4. Estimated coefficients of the NAI in each model for seedling survival. a Seedling survival ~ NAI +water + light, b seedling survival ~ NAI + water, c seedling survival ~ NAI + light, d seedling survival ~ NAI; x-axis radius k meters (30 ≤ k ≤ 300 per 5 m), y-axis weight of proximity l (0 ≤ k ≤ 2 per 0.05); a Seed maturation, b sound seeds, c predation by insects, d predation by vertebrates. Solid line indicates 0 (PDF 335 kb)
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Takeuchi, Y., Samejima, H., Nakagawa, M. et al. Neighborhood aggregation effect and its effective scale on reproductive success in Shorea laxa (Dipterocarpaceae). J Plant Res 123, 249–259 (2010). https://doi.org/10.1007/s10265-009-0265-1
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DOI: https://doi.org/10.1007/s10265-009-0265-1